Field of the Invention
The invention relates to a substrate which is made from paper and is provided with at least one integrated circuit.
A substrate of this nature is known from German Patent Application DE-196 01 358, and is used in security documents and banknotes to protect against forgery and fraud. This known substrate comprises an integrated circuit which is incorporated in the substrate and contains predetermined data. The IC is contactlessly readable and is joined to the substrate in a non-releasable manner. The IC which is used in this substrate is a conventional IC, i.e. of the well-known silicon type. The dimensions of the chip originally produced are reduced by means of etching or polishing, so that the chip acquires the thickness which is desired for it to be incorporated in the paper mass. In order to prevent damage to the crystalline circuits, the IC is reinforced with the aid of a support layer, which also serves to position the IC. Furthermore, the IC is covered with a protective, chemically resistant layer. The lack of flexibility of this known silicon chip is a drawback when a substrate of this nature is used as a security paper, for example in banknotes and identity documents. In addition, the extra layers which are to be included, as well as the additional processing step for producing the appropriate dimensions, lead to an additional increase in the cost price of a substrate of this nature.
The object of the present invention is to provide a paper-based substrate for use in security documents, banknotes and the like, in which an integrated circuit is incorporated, which substrate does not have the drawbacks mentioned above.
According to the present invention, this object is achieved with a substrate of the type mentioned above in which the integrated circuit comprises a semiconductive organic polymer. This means an electronic circuit which is arranged in the polymer material and the contents of which are programmed in order to assign it a specific function. Polymer chips of this nature are highly flexible and are therefore eminently suitable for use in security documents such as banknotes. Even sharp creases in the chip made from a semiconductive organic polymer do not impede the functioning of the chip. In addition, poly-meric ICs can be produced directly in the desired dimensions, in particular with regard to thickness, and the costs of a chip of this nature are lower by approximately a factor of 10 than the current lowest price for a chip of the silicon type.
In the polymeric chip, the nonconductive support on which the semiconductive polymer material is deposited substantially determines the thickness of the overall integrated circuit. It is preferable to use a mechanically strong insulator: plastics with strong intramolecular and intermolecular interactions are particularly suitable for this purpose.
Using an IC of this nature as a security mark in security paper and similar items provides novel and powerful means of protection, since producing these ICs is much too complicated for forgers and generally far exceeds their knowledge and capabilities.
In the context of this application, paper is understood to mean paper which is made from natural or synthetic fibres, as well as xe2x80x9cpaperxe2x80x9d which can nowadays be produced from plastic films, which paper is used for the production of security paper, banknotes and the like.
The integrated circuits may number one or more and may be adjusted as a function of the requirements. For example, with a view to certainty of operation, it is possible to incorporate two or more identical polymer chips, so that in the event of one of these chips failing the substrate and/or the end product which has been produced therefrom can still be used.